(1) Field of the Invention
This invention relates to a developing apparatus and development method for developing semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays and flat panel displays, and substrates for optical disks (hereinafter called simply “substrates”).
(2) Description of the Related Art
As one of the methods of developing resist film formed on surfaces of substrates, a puddle development mode is used widely (as disclosed in Japanese Unexamined Patent Publication No. 2003-109894, for example). This developing mode may be divided broadly into a developing process, a rinsing process and a drying process as described below.
First, a developer is supplied while moving a developer nozzle relative to a substrate, to form a puddle of the developer on the substrate. In this state, the substrate is maintained still for a predetermined period to allow for progress of a development reaction (developing process). Subsequently, the substrate is spun while supplying a rinsing liquid (e.g. deionized water) to the substrate to stop the development reaction and clean the substrate (rinsing process). After the rinsing process, the supply of the rinsing liquid is stopped and the substrate is spun at high speed to dry (drying process).
For this purpose, a developing unit has a spin-support device for rotatably supporting a substrate, the developer nozzle, and a rinsing liquid nozzle. A developing apparatus includes a plurality of such developing units to develop substrates in parallel.
(I)
However, a conventional apparatus having the above construction has the following drawbacks.
The surface of a substrate to be developed has resist film formed thereon, and generally has a large angle of contact (which is an angle between the substrate surface and a tangent to each droplet), and thus has a strong tendency to repel liquid. As the wavelength of exposing machines has become shorter from i-beam to KrF, and from KrF to ArF, the angle of contact of the substrate is becoming larger according to a resist material used. Moreover, considering the resist to be used in immersion exposure expected to be implemented in the near future, the angle of contact is likely to become still larger.
When the angle of contact of the substrate becomes large, there arises an inconvenience that the substrate cannot not be dried effectively. This aspect will be described with reference to FIGS. 1A, 1B and 1C. FIGS. 1A-1C are front views and plan views of a substrate in a rinsing process and a drying process in the prior art. FIG. 1A shows a state of a rinsing liquid being supplied from a rinsing liquid nozzle 71 to a wafer W in a spin. As seen, the rinsing liquid supplied onto the wafer W flows from the center to edges of the wafer W to be discarded outward from the wafer W. At this time, a film R of the rinsing liquid is formed on the wafer W.
FIG. 1B shows a state of the supply of the rinsing liquid being stopped and the wafer W being spin-dried. Most of the rinsing liquid forming the film R is discarded outward from the wafer W, but part thereof deforms into droplets on the wafer W. In FIG. 1B, the droplets are shown with sign “r” affixed thereto. The larger angle of contact of the wafer W has the greater tendency to form the droplets “r” of the rinsing liquid. When the droplets “r” of the rinsing liquid are sufficiently small, the centrifugal force produced by the spinning wafer W may fail to act on the droplets “r” of the rinsing liquid, thereby allowing the droplets “r” to remain on the wafer W. The components of the resist will dissolve in the droplets “r” of the rinsing liquid remaining on the wafer W. This results in an inconvenience that, as shown in FIG. 1C, the components of the resist dissolved in the droplets “r” of the rinsing liquid form deposits, which become post-develop defects “k”, on the wafer W having undergone a drying process.
(II)
The conventional method and apparatus have a drawback of requiring a long time for developing substrates. Among the respective processes of development, the developing process is the longest and takes up about a half of the total period of development. A development reaction which progresses in this developing process, specifically, is neutralization at development interfaces. With progress of the neutralization, the alkali concentration of the developer deteriorates (lowers). Consequently, the neutralization at the development interfaces slows down gradually. This deceleration is taken into consideration in determining a period for the developing process.
Since a long time is required for development, it is difficult to achieve a further improvement in the throughput of the developing apparatus. To increase the number of developing units in order to improve the throughput of the developing apparatus is unrealistic from the viewpoint of cost and footprint